As organic materials (e.g., organic waste materials) decompose in various systems (e.g., landfills (e.g., solid-waste landfills), wastewater treatment plants (WWTPs), agricultural waste facilities (e.g., livestock waste facilities), food waste digestion facilities, or other organic waste digesters), gases and other liquid byproducts are often generated. For example, with respect to landfills, the byproducts typically include landfill gas, condensate, and leachate. Landfill gas is a complex mixture of different gases created by the action of microorganisms within a landfill. Landfill gas typically includes approximately forty to sixty percent methane, with the remainder being mostly carbon dioxide. Other constituents of landfill gas may include oxygen, nitrogen, hydrogen sulfide, siloxanes, and some inert particulates. Land fill gas may also include trace amounts (e.g., less than 1%) of other volatile organic compounds (VOCs). Such trace gases may include a large array of species, but are typically mainly simple hydrocarbons.
Municipal Solid Waste (MSW) landfill owners and operators are required to comply with the Laws and Regulations of the United States Environmental Protection Agency's (EPA) Resource Conservation and Recovery Act (RCRA) which was enacted by Congress in 1976 to protect human health and the environment from the potential hazards of waste disposal, conserve energy and natural resources, reduce the amount of waste generated, and ensure that wastes are managed in an environmentally sound manner. RCRA, Subtitle D regulates the management of nonhazardous solid waste. It establishes minimum federal technical standards and guidelines for state solid waste plans in order to promote environmentally sound management of solid waste.
Depending on a variety of conditions, MSW owners may or may not be required to collect and destroy landfill gases. Some MSW owners collect and destroy landfill gas voluntarily, usually to control odors. Odors can diminish the value and potential use of land in the areas surrounding landfills, and the landfill footprint may not be returnable to a public use such as a park or nature trail.
Other MSW landfills are required to collect and destroy the landfill gas to destroy or diminish greenhouse gas emissions in compliance with EPA regulations. Many operating and closed MSW landfills that collect landfill gas and destroy the collected landfill gas do not attempt to provide a beneficial use of the collected landfill gas. Landfill gas if not collected, and either destroyed or processed into a beneficial use, results in release of greenhouse gases, including methane and carbon dioxide. Landfill gas can be a source of air pollution, and the associated leachate and condensate liquids can be water pollutants.
Currently, landfill utilization has multiple problems. For example, there is a lack of active and, in particular, closed landfills with systems in place capable of producing pipeline-quality biomethane. Because closed landfills typically produce landfill gas at a continuously declining rate, closed landfills may be essentially relegated to “dead land” as the declining annual production of gas constrains the ability to finance and recover, over a short time frame, large initial capital investments associated with implementing existing systems. Compounding this “dead land” model, landfills are highly regulated from an environmental standpoint. Air emissions, groundwater contaminants, methane migration, hazardous waste content in the biogas, and other impacts can make closed landfills unattractive for development. Additionally, pipeline utilities have been typically reluctant to accept landfill-produced biomethane for fear of introducing contaminants into their pipelines. Landfills typically differ from other biogas sources in that oxygen and nitrogen from the atmosphere can be present in the gas. Oxygen contamination is a significant problem for producing pipeline-quality biomethane, and nitrogen is also costly to remove.
Additionally, there has been a long felt need in the closed landfill industry for utilizing the landfill gas rather than just flaring off the landfill gas.